Levels are "a measurement of the Team's Credit to the League," says the tooltip for the feature, and they were added to Blaseball in Season 14.
The list of known levels is:
- Low A
- High A
Once a team reaches Low A, a small red blinking dot will appear next to a team's name, making them susceptible to attacks from the Consumers. The Consumers, which are shown as a shark in the game log, will attack a player on that team, causing them to lose overall star ratings.
What causes a team's Level to change is a complex series of statistical interactions around a Forbidden Knowledge stat called eDensity. More can be read about eDensity in FK:eDensity.